The present invention relates generally to telecommunications, and more particularly to network communications over public telephone switching systems.
FIG. 1 (background art) is a block diagram depicting the existing infrastructure 10 of the public switched telephone network (PSTN). Various devices may communicate via the existing infrastructure 10, and users today often have and use multiple such devices. In FIG. 1 a telephone 12a, facsimile 12b, modem 12c, computer 12d, and special service device 12e are shown connected to a PSTN 14 and another telephone 12a, facsimile 12b, modem 12c, computer 12d, and special service device 12e are shown also connected to the PSTN 14. The telephones 12a and facsimiles 12b are analog type devices which may communicate with respective like devices. In FIG. 1 the modems 12c stylistically depict the still common situation of digital devices (not shown) producing digital signals that are converted to and from analog type signals, but otherwise communicating using analog techniques. In contrast, the computers 12d and special service devices 12e shown here stylistically depict true digital type devices.
While the presence of computers 12d in the existing infrastructure 10 is relatively well known, some readers may not be familiar with the special service devices 12e. These are relatively common today, but little appreciated. Some examples include remote monitor able utility meters and alarm systems. Such special service devices 12e typically require a much lower data transfer rate than systems like the computers 12d. 
For communications between the respective sets of like devices, the analog xe2x80x9ctrafficxe2x80x9d may be entirely via the PSTN 14. In contrast, the digital traffic for the computers 12d may start on the PSTN 14 and then proceed via an Internet protocol network (IP network 18). Similarly, the digital traffic for the special service device 12e may start on the PSTN 14 and then proceed via a signal switching network, like the SS7 network 20 shown.
FIG. 2 (background art) is a block diagram depicting the most common digital, or xe2x80x9cInternet call,xe2x80x9d connection methodology. Digital devices (not shown here) produce digital signals which the modems 12c convert to analog type signals. The modems 12c connect to ingress switches 22 via conventional voice circuits or (commonly) plain old telephone service lines (POTS lines 24). The ingress switches 22 may connect directly to an egress switch 26, via POTS lines 24, or to a tandem switch 28 that further connects to the egress switch 26 via an interoffice trunk 30. The egress switch 26 is connected to an Internet service provider point-of-presence (ISP POP 32) via POTS lines 24. Often the ISPs will have multiple POTS lines 24 or ISDN primary rate interface configured into hunt groups, and this is the case depicted in FIG. 2. Finally, the ISP POP 32 connects to the IP network 18. Of course, digital communications going the other direction travel essentially the reverse path.
FIG. 3 (prior art) is a block diagram depicting the presently popular network evolution model, wherein the IP network 18 evolves to become a single common packet backbone. Analog devices like telephones 12a and facsimiles 12b (FIG. 1) have their signals converted to digital data packets. The same can be done for the analog output of modems 12c (FIG. 1), but would generally be pointless. Existing digital devices like the computers 12d would continue to connect to the IP network 18, and the special service devices 12e would evolve into types that could also connect to the IP network 18. New digital audio-video devices, like digital voice phones 12f and video units 12g (e.g., cameras, or xe2x80x9cCAMsxe2x80x9d as they are often termed in the industry) can similarly connect directly to the IP network 18. Unfortunately, there are problems with this evolution model. In particular, and as discussed more extensively elsewhere herein, it obsoletes the current investment in PSTN technology and it introduces a number of transitional technical problems.
FIG. 4 is a block diagram depicting a more suitable network evolution model. The various communications devices (12a-g) connect to an access network 34, and the access network 34 connects to the PSTN 14 (essentially the major central element already in the existing infrastructure 10), the IP network 18, the SS7 network 20 and also a broadband network 36. The IP network 18 can handle most existing bandwidth digital communications, and the broadband network 36 can handle high bandwidth communications such as digital video. Under this alternate network evolution model the broadband network 36 would initially be optional, and only added as needed.
FIG. 5 (background art) is a block diagram of a conventional current digital loop carrier communications architecture (DLC architecture 40). At a customer premises 42 a LAN 44 includes network devices 46 and what will here be termed customer premises equipment (CPE 48; such as a channel service unit/data service unit, analog/ISDN/xDSL type modems etc.). The customer premises 42 may also include plain old telephone service (POTS) devices, such as the telephone 12a which is shown.
The next segment in the communications architecture is the local loop 50. It primarily includes a remote terminal 52. Connecting digital traffic from the CPE 48 to the remote terminal 52 is one or more T1/E1/DSx lines 54 (which here may generically include all digital xe2x80x9ccopper wirexe2x80x9d protocols as well, e.g., xDSL and ISDN). Carrying analog (e.g., voice, facsimile, and modem) POTS traffic to the remote terminal 52 are one or more POTS lines 24. A plurality of such customer premises 42 is typically serviced by each remote terminal 52.
Following this in the communications architecture is the central office 56, which includes a central office terminal 58 that connects to a central office switch 60 (larger central offices typically include multiple central office terminals 58 and multiple central office switches 60, and central offices may even have remote terminals 52 directly connected into the central office switches 60). Optionally, Internet routers 62 from Internet service providers (ISP""s), may also be connected to the central office switch 60.
For simplicity in discussion, the Internet is used as a generic example of a specialized application network here, but it should be appreciated that many other examples exist. Alarm systems and video conferencing networks are two common ones, and ones which might respectively use the SS7 network 20 (FIGS. 1 and 4) and the broadband network 36 (FIG. 4). For convenience in discussion, such dispersed networks that operate through, or in some segments parallel to, the public telephone switching system are herein termed wide area networks (WAN 64).
Continuing with FIG. 5 (background art), a plurality of local loops 50 are typically serviced by each central office terminal 58, and a plurality of specialized networks devices (e.g., Internet routers 62) may be serviced by each central office switch 60. Today, the remote terminal 52 to central office terminal 58, the central office terminal 58 to central office switch 60, and the central office switch 60 to Internet router 62 connections are typically all also T1/E1/DSx lines 54. FIG. 5 includes the specialized network example of an ISP""s Internet routers 62 in turn connected to other devices (not shown) by a 10/100/1000 base-T line in the WAN 64. This example presumes the modern practice of directly connecting specialized network devices directly to the central office switch 60 with T1/E1/DSx lines 54. Older installations, smaller ISP""s, and other specialized networks may still employ modem banks.
Within this conventional architecture, the recent approach to increasing switching system bandwidth has been development of new technologies. One example is digital subscriber line (xDSL). It increases existing copper wire bandwidth, but by adding yet another set of protocols. It also address the problem in only one segment of the communications architecture, the customer premises 42 to local loop 50 segment, thus making it a stratified approach. This approach uses asynchronous transfer mode (ATM), which requires new hardware throughout the entire communications architecture, and is therefore not a stratified approach. ATM also requires fixed length packets, which is not always efficient when dealing with a variety of data types. ATM may hold great promise for the ultimate future, but it is definitely not an interim or inexpensive solution.
FIGS. 6a-b (prior art) are block diagrams of a current digital subscriber line (xDSL) architecture, wherein FIG. 6a depicts the hardware architecture and FIG. 6b depicts the software architecture. In FIG. 6a, at the customer premises 42 a computer 12d employs an ATM transmission unitxe2x80x94remote (ATU-R 66) to connect via an xDSL interface 68 to an ATUxe2x80x94central (ATU-C 70) in a DSL access multiplexer (DSLAM 72) at the telco central office 56. Further connection is then made via an asynchronous transfer mode network (ATM 74) to a broadband access server (BAS 76) at a network service provider 78. In FIG. 6b, at the customer premises 42 a network protocol 80, point-to-point protocol 82, an ATM adaptation layer (AAL584), ATM protocol 86, and asynchronous DSL protocol (ADSL protocol 88) are employed. At the central office 56, the ATM protocol 86 and the ADSL protocol 88 are employed along with a physical protocol 90. At the network service provider 78, another (layer) physical protocol 90, ATM protocol 86, AAL584, point-to-point protocol 82, and a network protocol 80 are employed. Some of these layers may be the same and some may be different. For example, the physical protocols 90 usually must be the same on adjacent nodes, and the network protocols 80 usually are the same correspondent nodes.
In summary, the communications architecture used today is quite complex, and getting more so. A myriad of different networks and protocols is already in use, with some being gradually grand-fathered out and emerging new ones growing in importance. It is simply not realistic to expect that old systems will be instantaneously replaced with new ones, and it follows that what is needed are systems for graceful upgrade. Such systems should permit incorporation of both the existing systems and those which are emerging and even yet to be developed.
Accordingly, it is an object of the present invention to provide a system to upgrade existing public switched telephone network (PSTN) systems to additionally handle packet transfer communications traffic.
Another object of the invention is to provide a system for reducing or eliminating local loop bottlenecks in existing PSTN systems without resorting to parallel packet switching networks.
And another object of the invention is to provide efficient high-bandwidth packet transfer public networks leveraging much of the existing PSTN infrastructure and investment.
Briefly, one preferred embodiment of the present invention is an improved communications system of the type in which a public switched telephone network (PSTN) has both circuit switched and packet transfer communications device types at various customer premises connected through at least one telco central office. The improvement includes an access network having an access concentrator located at a customer premises, a remote concentrator located between the customer premises and the telco central office, and a transfer switch located at the telco central office. The access concentrator accepts both the switched signals packet signals from the communications devices and communicates them as a terminating node signal over a internal interface to a remote concentrator. The remote concentrator accepts the terminating node signal from the access concentrator and communicates it as a distributor node signal over another internal interface to the transfer switch. The transfer switch accepts the distributor node signal from the remote concentrator and separates the switched signals and the packet signals from the distributor node signal. The transfer switch then transmits the switched signals onward to their ultimate intended circuit switched type communications devices. And the transfer switch also routes the packet signals onward to their ultimate intended packet transfer type communications devices.
An advantage of the present invention is that it permits efficient, and therefore highly economical, integration of both circuit switched and packet transferred network traffic onto a network backbone based around the existing PSTN system.
Another advantage of the invention is that it permits packet transferred network traffic to be particularly efficiently sent by employing spoofing of network control packages, e.g., media access control (MAC) addresses, across the local loop of the communications network and thus reduce or eliminate the need to transfer this information.
Another advantage of the invention is that it integrates existing and emerging analog and digital systems for computer and other data, voice, and video.
And, another advantage of the invention is that it reduces peripheral communications problems like the current IP address shortage, network security, unifying directory services, and providing additional number services in our finite numbering schemes.
These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawings.